LONDON European leaders will hold an unprecedented vote on whether Jean-Claude Juncker becomes the next president of the European Commission after Prime Minister David Cameron insisted on such a ballot on Monday, Cameron's office said.
For the first time, the leader's spokeswoman refused to rule out the possibility that he would recommend a "No" vote to staying in the European Union in a referendum he has promised for 2017 if he is re-elected next year.
Cameron's demand for a vote on Juncker, made at a tense meeting with European Council President Herman Van Rompuy, sets the stage for an ill-tempered showdown when EU leaders meet in Belgium to discuss the matter on Thursday and Friday.
The outcome could highlight Britain's isolation and show voters back home that the prime minister, under pressure from Eurosceptics in the rising UK Independence Party and his own Conservative party, is determined to fight to change the EU.
However by raising the stakes in a battle he cannot win, Cameron risks pushing Britain closer towards the EU's exit.
"The talks were full and frank," Cameron's official spokeswoman said of the meeting with Van Rompuy, in language indicating the session, which the BBC said lasted just 30 minutes, had been acrimonious. "The prime minister explained that his view would not change.
"The prime minister asked President Van Rompuy to prepare the European Council for a vote on Mr Juncker's nomination, should the European Council choose to depart from a consensus-led approach when it meets this week," she said. Van Rompuy had agreed "to work through how a vote would proceed".
Van Rompuy's office declined to comment. Pictures of the meeting released by Cameron's office suggested a strained atmosphere with both men unsmiling.
Cameron told reporters before the meeting he was determined to put fellow European leaders on the spot so they would have to "make up their mind whether to do what their heart and head tell them or not".
His confrontational strategy reflects deep frustration in London after the collapse of efforts to build an alliance against the 59-year-old former Luxembourg prime minister, a veteran centre-right EU deal-broker.
Asked whether Cameron was threatening to campaign for a "No" vote, the spokeswoman earlier told a briefing: "The elected national leaders of the European council need to think about the fact that over the next 2-1/2 years, if the prime minister is re-elected and therefore there is a referendum in this country, that clearly the decisions taken by the EU in that period will affect British voters' views of the EU and is likely to affect the way they vote in any such referendum."
Britain believes Juncker's federalist views mean he is not the right person to drive reforms that Cameron has promised to deliver before giving Britons an in/out vote in 2017. London also argues that EU leaders should have a free hand in nominating a candidate, and not yield to the European Parliament's preference as in Juncker's case.
EU summit decisions are usually taken by consensus and many EU insiders say Cameron's tactics have been deeply misguided, betraying a misunderstanding of the consensual way in which the 28-nation bloc works.
His strategy took another knock on Monday when a Polish magazine published a transcript of a recorded conversation between top Polish politicians about him. According to the transcript, Foreign Minister Radoslaw Sikorski criticised Cameron's attempts to renegotiate EU rules on freedom of movement of workers as "reckless", saying it showed Cameron's "incompetence in European affairs". Cameron's spokeswoman declined to comment. Poles make up the largest community of foreign workers to have settled in Britain since the EU enlarged to the east in 2004.
The meeting between Cameron and Van Rompuy was unusually short. In contrast to many other leaders, Cameron did not invite the man who chairs EU summits to lunch, serving only coffee and biscuits as they discussed the summit preparations.
Van Rompuy has sent EU leaders a draft strategic agenda for the EU for the next five years which he wants the summit to approve later this week.
The document, seen by Reuters, touches on some issues of concern to Britain such as restraining the EU's reach into daily life but does not include proposals pushed by Cameron to reduce Brussels' powers, give national parliaments a veto over EU legislation or scrap some existing business regulation.
It plays down the scale of what Cameron calls "welfare tourism" - migrants from poorer EU countries who claim benefits in richer host countries - and offers no prospect of dropping the EU's treaty goal of "ever closer union".
Earlier, Chancellor George Osborne, Cameron's right-hand man, accused EU leaders of duplicity, suggesting they were being supportive of Juncker publicly but negative privately.
"I think there's a rather odd phenomenon at the moment which does happen believe it or not in politics which is people are saying quite a lot of things privately which they're not saying publicly," Osborne told BBC radio.
Aides have said Cameron thought from private discussions that some other EU leaders shared his views about Juncker, a 25-year veteran of EU summits, and agreed with him on the flawed nature of the selection process.
On Sunday, Iain Duncan Smith, minister for work and pensions, said Cameron had told him that Germany and Italy harboured concerns about Juncker's suitability for the job too.
But he said they felt obliged to back him because of promises they had made before last month's European elections in which Eurosceptic parties prospered in Britain and elsewhere.
"If they give Jean-Claude Juncker a job, this is like literally flicking two fingers at the rest of Europe and saying to all the people out there 'we know that you voted the way did, but you're wrong and we're just going to show you how wrong you are by carrying on as though nothing happened'," he said.
In Britain, raising two fingers is an obscene gesture.
(Additional reporting by William James and Kylie MacLellan in London and Paul Taylor in Paris; Editing by Tom Heneghan and Paul Taylor)
Our top photos from the past week.